Electrostatographic flexible imaging members are well known in the electrostatographic art. Typical flexible electrostatographic imaging members include, for example, (1) photosensitive members (photoreceptors) commonly utilized in electrophotographic (xerographic) processes and (2) electroreceptors such as ionographic imaging members for electrographic imaging systems. The flexible electrostatographic imaging members may be seamless or seamed belts. Typical electrophotographic imaging member belts comprise a charge transport layer and a charge generating layer on one side of a supporting substrate layer and an anticurl backing layer coated on the opposite side of the substrate layer. A typical electrographic imaging member belt does however have a more simple material structure; it comprises a dielectric imaging layer on one side of a supporting substrate and an anticurl backing layer on the opposite side of the substrate.
In a machine service environment, a flexible imaging member belt mounted on a belt supporting module is generally exposed to repetitive electrophotographic image cycling which subjects the outer-most charge transport layer to mechanical fatigue as the imaging member belt bends and flexes over the belt drive roller and all other belt module support rollers, as well as sliding bending contact above each backer bar""s curving surface. This repetitive imaging member belt cycling leads to a gradual deterioration in the physical/mechanical integrity of the exposed outer charge transport layer leading to premature onset of charge transport layer fatigue cracking. The cracks developed in the charge transport layer as a result of dynamic belt fatiguing are found to manifest themselves into copy printout defects which thereby adversely affect the image quality on the receiving paper. In essence, the appearance of charge transport cracking cuts short the imaging member belt""s intended functional life.
When a production web stock consisting of several thousand feet of coated multi-layered photoreceptor is obtained after finishing the charge transport layer coating/drying process, it is seen to spontaneously curl upwardly and required an anticurl backing layer applied to the backside of the substrate support, opposite to the side having the charge transport layer, to offset the curl and render flat the photoreceptor web stock. The exhibition of upward photoreceptor curling after completion of charge transport layer coating has been determined to be the consequence of thermal contraction mismatch between the applied charge transport layer and the substrate support under the conditions of elevated temperature heating/drying the wet coating and eventual cooling down to room ambient temperature. Since the charge transport layer in a typical photoreceptor device has a coefficient of thermal contraction approximately 3xc2xd times larger than the substrate support, it does, upon cooling down to room ambient temperature, result in greater dimensional contraction than that of the substrate support causing upward photoreceptor curling which thereby requires the anticurl backing layer to balance the curl and provide flatness.
Although it may be useful in certain situations to have the anticurl backing layer to complete a typical photoreceptor web stock material package, nonetheless the application of anticurl backing layer onto the backside of the substrate support (for counter-acting the upward curling and rendering flat the photoreceptor web stock) has caused the charge transport layer to instantaneously build up an internal tension strain of about 0.28% in its material matrix. After converting the web stock into a seamed photoreceptor belt, the internal built-up strain is then cumulatively adding onto each photoreceptor bending induced strain as the belt flexes over a variety of belt module support rollers during photoreceptor belt dynamic cyclic function in a machine. The consequence of this compounding strain effect is an early onset of the charge transport layer fatigue cracking problem which then leads to undesirable printout defects in the final image copies.
Thus, there is a need, addressed by the present invention, for new methods to reduce or eliminate the built-up internal tension strain that can occur in certain flexible multi-layer members to enhance the mechanical properties of the members.
Conventional multi-layer members and methods for treating such members are disclosed in: Yu et al., U.S. Pat. No. 6,165,670; Yu et al., U.S. Pat. No. 5,606,396; Yu, U.S. Pat. No. 5,089,369; Yu, U.S. Pat. No. 5,167,987; and Yu, U.S. Pat. No. 4,983,481.
The present invention is accomplished in embodiments by providing a method of treating a flexible multi-layer member exhibiting a glass transition temperature and including a surface layer, the method comprising:
moving the member through a member path comprising: a contact zone defined by contact of the member with an arcuate surface including a curved contact zone region; a pre-contact member path before the contact zone; and a post-contact member path after the contact zone;
heating sequentially each portion of the surface layer such that each of the heated surface layer portions has a temperature above the glass transition temperature while in the curved contact zone region; and
cooling sequentially each of the heated surface layer portions while in the contact zone such that the temperature of each of the heated surface layer portions falls to below the glass transition temperature prior to each of the heated surface layer portions exiting the curved contact zone region, thereby defining a cooling region, wherein the heating is accomplished in a heating region encompassing any part or all of the contact zone outside the cooling region and a portion of the pre-contact member path adjacent the contact zone.
There is also provided in embodiments a method of treating a flexible imaging member comprised of in the following sequence a substrate layer, a charge generating layer, and a charge transport layer wherein the charge transport layer exhibits a glass transition temperature, the method comprising:
moving the member through a member path comprising: a contact zone defined by contact of the member with an arcuate surface including a curved contact zone region; a pre-contact member path before the contact zone; and a post-contact member path after the contact zone;
heating sequentially each portion of the charge transport layer such that each of the heated charge transport layer portions has a temperature above the glass transition temperature while in the curved contact zone region; and
cooling sequentially each of the heated charge transport layer portions while in the contact zone such that the temperature of each of the heated charge transport layer portions falls to below the glass transition temperature prior to each of the heated charge transport layer portions exiting the curved contact zone region, thereby defining a cooling region, wherein the heating is accomplished in a heating region encompassing any part or all of the contact zone outside the cooling region and a portion of the pre-contact member path adjacent the contact zone.